1. Field of Use
This invention relates generally to oil separator and gas pressure equalizer means for reciprocating gas compressors.
2. Description of the Prior Art
A typical multicylinder reciprocating type gas compressor comprises a housing having a partition member therein which divides the space within the housing into an upper suction chamber and a lower crankcase chamber, the lowest portion of which serves as an oil sump. The partition member is provided with relatively large openings in which cylinder sleeves are mounted and pistons are slidably mounted for reciprocating motion in the cylinder sleeves to compress gas passing through the suction chamber. The pistons are connected by piston rods, which are provided with piston rod bearings, to a crankshaft which is rotatably mounted on crankshaft bearings in the lower crankcase chamber. The partition member also supports capacity reduction mechanisms which are located in the upper suction chamber and which operate gas inlet valves which are located at the upper ends of the cylinder sleeves. Each capacity reduction mechanism, which operates one or more gas inlet such valves, is hydraulically controlled by hydraulic fluid which flows through a hydraulic fluid line which extends through a relatively small opening provided in the partition member. In some prior art compressors, the partition is also provided with a small pressure equalizer or vent hole which serves to provide for gas pressure equalization between the suction chamber and the crankcase chamber and thereby improve the efficiency of the refrigeration system.
Furthermore, some gas leaks past the seals for the large and small openings through the partition member.
During compressor operation, lubricating oil is supplied under pressure through passages in the housing, crankshaft and piston rods to the piston rod bearings and crankshaft bearings in the crankcase. As oil drains out of the bearings during crankshaft rotation, oil droplets are flung about the crankcase chamber and eventually drain into the oil sump from whence the oil is recovered and recirculated. Because of the "blow-by" phenomena which occurs as the pistons compress the gas, some gas leaks past the pistons and rings and tends to pressurize the crankcase. As this gas is vented back to the suction chamber, it carries oil mist through the vent hole into the suction chamber where they mix with the gas being drawn into the cylinders compressed and expelled into the system. This is undesirable for two reasons. First, most of such oil is lost into the refrigeration system and is no longer available in the sump for lubrication purposes. Over time, the amount of oil lost is substantial and is costly to replace. Second, such oil contaminates both the refrigerant gas and the refrigeration system and reduces system efficiency.
As a practical matter, some of the oil mist coalesces in the suction chamber and collects on the partition but is able to drain back into the crankcase chamber through the pressure equalizer hole and into the oil sump therein. However, oil dripping or draining through the pressure equalizer hole falls onto the rotating crankshaft and is flung about the crankcase chamber in the form of mist causing some mist to be expelled up through the pressure equalizer hole back into the suction chamber.